Bacterial infections that exist as single independent cells are referred to as planktonic, and are generally treated with antibiotics depending on relatively fast and accurate diagnoses. In contrast, a biofilm is an accumulation of bacteria embedded in a polysaccharide matrix, which adheres to a biologic or non-biologic surface. The formation of biofilm is a significant medical problem, accounting for over eighty percent of microbial infections in the body. Examples include infections of indwelling catheters, cardiac implants, prosthetic heart valves, synthetic vascular grafts and stents, internal fixation devices, prostheses, synthetic mesh, tracheal and ventilator tubing, oral soft tissues, dental implants and teeth, middle ear, gastrointestinal tract, airway/lung tissue, eyes, urogenital tract, urinary tract prostheses, peritoneal membrane and peritoneal dialysis catheters, and percutaneous sutures. Bacteria within biofilms have increased resistance to antibiotics, even though these same bacteria are sensitive to antibiotics if grown under planktonic conditions. The matrix of extracellular polymeric substances (EPSs) has an essential role in defining the cohesiveness and other physical properties of these adherent microbial communities. Additionally, biofilm growth increases the opportunity for gene transfer between bacteria, therefore further perpetuating antibiotic resistance. Recent studies have shown that extracellular DNA, secreted by bacteria, prevent efficient drug delivery to the biofilms. Control of biofilm persistence and growth is thus problematic due to increased resistance to treatment with antibiotics as compared to planktonic cells.
Use of a synthetic mesh is currently the most common repair material used for reinforcement of ventral hernias. Mesh infection is an example of a type of implant infection in which surgical removal and debridement can result in significant morbidity for patients. Two million Americans undergo abdominal surgery annually with a postoperative incisional hernia rate of 10 to 23 percent. About 400,000 ventral hernia repairs are performed each year in the United States alone, with reported hernia recurrences in 40 to 50 percent of cases. Synthetic mesh reinforces hernia repairs and has been shown to decrease recurrences compared to primary repair alone. However, morbidities related to mesh infection can limit efficacy. Reported mesh infection rates range from 4 to 16 percent. Known mesh complications include infection requiring prolonged antibiotic coverage, surgical debridements, and mesh explantation. Postoperative mesh infections requiring debridement and mesh explantation continue to be devastating problems for patients, and a reconstructive challenge for surgeons.
Multiple pathways may lead to infection of synthetic mesh. Patients may have an acute postoperative mesh infection, or dehiscence of the wound may expose the mesh, leading to colonization and infection of the prosthesis. Reoperation through synthetic mesh may also lead to infection. Additionally, seromas that develop may become infected, leading to subsequent contamination and removal of the prosthesis. The bacteria that commonly infect mesh are methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, Escherichia coli, Proteus mirabilis, Prevotella bivia, and Pseudomonas aeruginosa. Antibiotics alone are not an effective treatment for mesh infections.
Techniques for promoting biofilm detachment with chemical and enzymatic agents that attack the EPS matrix have been investigated with variable and overall disappointing results. Because there is no effective treatment for biofilm infections, the gold standard treatment is mechanical removal of the infected material and/or tissue. But mechanical removal is not always possible without risk of serious complications. If the biofilm infected material cannot be removed, the patient is placed on chronic suppressive antibiotics, therefore requiring several different antibiotics at high doses for an extended period of time. This may induce further resistance, tolerance, and eventually chronic infection.
What is needed is a non-antibiotic based intervention that addresses biofilm infections and reduces emerging microbial resistance to multiple drugs.